This invention relates to line protectors for communications circuits, and more particularly to a protector commonly known in the art as a central office protector. Protectors of this kind are used to protect inside plant or central office equipment from surge voltages and overcurrent faults that may appear on incoming lines as a result of power line faults, lightning or the like.
Many central office protectors are designed to provide protection against overcurrent faults that may result from low voltage or "sneak" currents. These sneak currents can damage the protector or the equipment to be protected. As a result, many central office protectors embody heat coils which become heated in an overcurrent condition on the line. The heat generated by the heat coil is applied to solder that melts and releases a mechanism to cause the line to become grounded. However, there are numerous telephone installations in which the cables are underground where they are isolated from power lines or other potential sources of faults that cause sneak currents, and as a result line protectors for such telephone systems often do not require heat coils.
Line protectors of the foregoing type are generally constructed in the form of modules which are plugged into termination members or connectors which are, in turn, mounted on a telephone main distribution frame. In many urban areas with rapidly expanding telephone systems there is a problem of finding suitable floor space for all of the termination structure for the central office. With space at a premium it is important that the protector module be as compact as is reasonably possible and still be dependable in operation.